It is well known that "green" or unfired bricks and similar objects require a drying treatment in the course of their production and that the drying conditions will vary depending on the type of brick or object involved. For example, extruded bricks are often stacked prior to firing on tunnel kiln cars directly after being formed. The cars are then pushed through a tunnel dryer which has been provided with exhaust means in the tunnel drying space, generally at the entrance end, i.e., directly adjacent to the opening through which the tunnel kiln cars enter the tunnel.
Heretofore, drying tunnels have incorporated exhaust means whereby the exhaust air is drawn off through exhaust openings disposed in the roof area of the drying space without any additional exhaust means or means for controlling the air flow. Such arrangements often produce uneven drying of the bricks due to the increased flow of air along the roof (due in part to non-uniform air temperatures within the tunnel), resulting in longer drying times and, in the worst cases, damage to the bricks or ware being dried.
The present invention substantially eliminates the uneven drying problems encountered in prior art systems by utilizing a tunnel drying design having exhaust means and means for controlling the air flow within the tunnel which result in improved uniformity and efficiency of the drying process.
The particular advantages achieved by the present invention include the following. In an exemplary tunnel dryer according to the invention, the air flow along the roof of the tunnel is modified and is controlled by exhaust means which result in a more uniform and efficient drying operation. The control of the air flow is accomplished by means of one or more adjustable partitions disposed within the tunnel at preselected locations which limit and direct the cross-sectional flow of air in the region where the ware is undergoing drying. As such, the present invention prevents unwanted air flow along the roof and redistributes the air stream within the tunnel. In particular, the adjustable partition according to the invention modifies the air circulation to prevent an increased flow of higher temperature air along the tunnel roof. It is also possible to modify the air flow rate to suit various drying requirements and thereby substantially reduce the time required for the drying process since all cars, including the very first car entering the tunnel, can be subjected to a constant stream of dry air which is more uniform in temperature and flow rate. The adjustable partition in accordance with the invention may also be raised or lowered during the drying operation or after the drying is completed in order to provide the necessary cross-sectional area for loading and unloading the dryer. The partition can also be adapted to different loading heights for the cars carrying the ware to be dried, depending on the specific type and amount of materials involved.
The preferred embodiment of the present invention utilizes one or more single-piece partitions which may be vertically adjusted to extend through one or more recesses in the roof of the tunnel dryer. Specifically, means are provided whereby a partition (or partitions) can be adjusted to any vertical height within the tunnel. At its highest point of adjustment, the bottom edge of a partition will be positioned at the top of the roof line. In such a position, the partition will release the full cross-sectional area of air flow into the tunnel. In the preferred embodiment, seals may be provided between the recess and the partition to prevent the ingress of "secondary air" into the tunnel. No seals are required, however, if a housing is disposed on the roof to provide a tight seal around the recessed area. The height of such a housing must be such that it will accommodate any desired portion of the adjustable partition. If, for example, a partition is used to release substantially the full height of the air flow within the tunnel, the height of the housing must be substantially equal to the height of the partition itself.
As those skilled in the art will appreciate, various possibilities exist for the disposition of the exhaust system and adjustable partitions within the tunnel. For example, a single ventilation or exhaust system may be placed in the middle of the tunnel. In that case, two partitions in accordance with the invention would be required, with each partition disposed on either side of the ventilation or exhaust means.
Thus, it is an object of the present invention to provide for a tunnel dryer which will improve the efficiency and uniformity of the drying process.
It is a further object of the present invention to provide means for controlling the air flow within a tunnel dryer to make the air more uniform in temperature and flow rate.
It is still a further object of the present invention to provide a tunnel dryer which will reduce the drying time and reduce the possibility of damaged or non-uniformly dried ware. These and other objects of the present invention will be made more clear from the following description taken in conjunction with the appended drawings.